Category Archives: biology

Editing Genes Using Molecular Scissors

Friends,

In the last few years a revolutionary new technique has been developed to edit genes. In this VERITAS I will describe the technique and how it has the potential to completely transform the way we fight diseases and how it may help us come up with new disease resistant varieties of plants and animals.

Continue reading Editing Genes Using Molecular Scissors

An ugly little animal may help us beat cancer and change our perception about society

Friends,

Today I will tell you about an amazing little creature. When you ask someone to name an amazing animal or a spectacular creature, they would most likely name lions or tigers or some other large creature. Indeed, most symbols that are based on animals tend to be based on a few animals- the same few animals have been used repeatedly in history and in romantic or magical tales. But today I will tell you about a little creature which does not look as spectacular as a tiger, nor does it have the strength of an elephant and it is not as beautiful as a butterfly. It is a small, ugly animal. But, I hope to convince you in this VERITAS that it is an amazing animal. So amazing that Science magazine named it “Vertebrate of the year” in 2013.

I am talking about the naked mole rat. If you search for its pictures on the internet, you will agree that it is pretty ugly and not so impressive to look at. But it has some characteristics which make it one of the most remarkable creatures that exist. But before we go into these remarkable characteristics, let’s talk about the more “commonplace” characteristics. The naked mole rat, as the name suggests, lacks hair on its body. It is 8-10 cms long and weighs about 30-35 grams. It has tiny eyes and its eyesight is very poor- so basically the eyes just help detect darkness and light. It does not need to see because it spends its entire life underground. Colonies of naked mole rats live in a complex system of subterranean tunnels in the arid and semi-arid regions of East Africa. The colonies can contain upto 300 individuals( the average size is 80 individuals) and the tunnel systems can be several kilometers long.

Now, let’s talk about the characteristics that make this an amazing creature. So amazing that it does deserve the “Vertebrate of the year” title that Science gave it in 2013. Let me first list the amazing characteristics and then explain each one of them in detail: social behavior, thermo-conformance, resistance to cancer, lack of pain and extraordinary life span.

  • Social Behaviour: Bees, Ants, Wasps and Termites live in what we call Eusocial societies- In Greek Eu means real or good. So Eusocial societies display the highest form of social behavior. Eusocial societies have a single breeding female and the rest of the females are workers/defenders. So there is a complex division of labour.  For a long time scientists believed that Bees, Ants, Wasps and Termites are the only species that display eusociality. Now, all these are insects and wasps, bees and ants belong to the same order. So scientists believed that eusocial societies are the result of certain genetic characteristics. But then they discovered the naked mole rat. Now, the naked mole rat is a mammal and is very far genetically from bees and ants but still it displays eusocial behavior. This was an amazing discovery and scientists realized that social systems in species may arise out of environment factors or evolutionary pressures. It is now understood that since living conditions for naked mole rats is very difficult so the only way they can survive is by living in large families in which some individuals do nothing else but find food, others only defend the family from predators( like snakes) and the queen only reproduces. If each individual reproduced, the family would not survive because of the competition and also because reproduction is costly in terms of time and energy and digging tunnels and finding food needs a lot of energy. So most individuals are not involved in reproduction at all and they just support the queen who has very similar genes to them- the genes are being passed on through the queen and not each individual. To give you an idea of how difficult it is for mole rats to find food consider this: naked mole rats eat tubers and sometimes the tubers are very far away from the mole rat tunnels. They do not come out of their tunnels but need to tunnel to the tuber. The tuber gives out no smell and the naked mole rats have very bad vision. So they are blindly searching for tubers by digging tunnels in all directions. No single individual can survive like this. They can succeed only if they make huge teams and dig in all directions; even then it may take them several weeks to find a tuber. Therefore the amazing fact that naked mole rats has told us is that the formation of societies and social structures is not just related to genes- there is a very strong environmental influence as well.
  • Thermo-conformance: Animals have an internal body temperature which they need to maintain in spite of the temperature of the environment outside. For example, we humans have the internal body temperature of about 37 degrees C and we need to maintain that using internal processes( like sweating, shivering etc). In other words, we humans are thermo regulators because we need to maintain a specific internal body temperature. All animals that are thermo-regulators can be divided into two kinds: warm blooded- those who can maintain temperature using internal processes and cold blooded- those that need to maintain their body temperature by moving to warm/cool areas. But naked mole rats have solved the temperature problem in a very interesting and “innovative” manner- the naked mole rat just adapts to the temperature of the environment outside! So it is not a thermo regulator, it is a thermo-conformer. Thermo conformers are very rare- the naked mole rat is the only mammalian thermo-conformer.
  • Immunity to Pain: Almost all animals experience pain when their skin comes in contract with acid or capsaicin( the stuff that gives “heat” to chili peppers). This is due to a neurotransmitter known as substance P which is present in the skin. The naked mole rat does not have substance P and is thus immune to the pain of acid or the burning sensation caused by capsaicin. P substance also causes long term inflammation in injuries and also after surgery. Thus, scientists are studying the naked mole rat to get some clues on how this pain can be managed/reduced. This is a very important field of study. There are people who live in chronic pain eveyday of their lives and we need a way to help them. The naked mole rat may offer us some clues. Note that the pain of inflammatory diseases like Arthritis is also caused because of acid buildup in tissues- so the research on naked mole rat’s pain immunity is directly applicable. Now, lets ask why the naked mole rat is immune to acid pain? It lives in deep tunnels in large groups so there is a carbon dioxide buildup inside the tunnels. We breathe air that has less than .1% C02. The naked mole rat lives in tunnels in which C02 can reach upto 10%. And C02 causes acid buildup in body tissues. So the naked mole rat evolved to be immune to the pain caused by this acid buildup.
  • Resistance to Cancer:  In all creatures Nature has mechanisms in place to control cell growth and division. A single cell moves freely and multiples without any inhibition. But when a normal cell comes in contact with another cell, it stops multiplying and tries to move away. This prevents cells crowding in a small area. The aim of nature is to stop growth when there is no space to grow and to not have cells crowd into a small area. This is called contact inhibition. But cancer cells do not have the property of growth inhibition and keep growing even when they are crowded into a small space. They keep growing even when there is no space- they grow on top of each other. Almost all animals can develop these cancer cells. But, not our amazing naked mole rat. Scientists have never found a mole rat that has cancer! And the reason is that the cells of the mole rat are hyper sensitive to contact inhibition. Or, in other words, the cells of a naked mole rat are much more likely to stop dividing when they come into contact with other cells than any other creature. In most creatures the gene p27 is responsible for contact inhibition. But in the naked mole rat there is an additional gene p16 which is even more active and prevents overcrowding at much lower population densities than p27. So even if one of the gene( p16 or 27 ) fails, the other still prevents overcrowding and cell division during crowding and thus prevents cancer. In humans we have only p27 responsible for growth inhibition and if that fails, we get cancer. Scientists are trying to understand the cancer resistance of naked mole rats and want to use that research to find a way to prevent cancer in humans.
  • Long Lifespan: A common mouse or rat lives for about 4 years. The naked mole rat can live upto 30 years. In the rodent world the naked mole rat is the longevity world champion. Ageing is caused by oxidative stress. Oxidative stress refers to the buildup of free radicals in the cells of our body. Free radicals come from metabolic processes in our body but these are harmful. Our body has ways of dealing with free radicals( basically a kind of detoxification) but over time the balance between creation of free radicals and their destruction is lost and there is a buildup of free radicals or, in other words, oxidative stress occurs. The naked mole rat has a very interesting way of dealing with this oxidative stress. Its metabolic processes become very slow when there is less food. During these times, therefore, the production of free radicals is dramatically reduced. Thus by controlling its metabolism and making it very slow for long periods the naked mole rat avoids oxidative stress for a longer period of time and lives a very long life. Oxidative stress is also responsible for diseases like Parkinson’s, Alzheimer and other age related disorders. Thus finding out why the naked mole rat lives longer may give us clues to cure these widespread and debilitating diseases.

Isn’t the naked mole rat an amazing creature? From it we may learn how to live longer, have less people suffer from Alzheimer’s disease, cure cancers( or prevent them from happening) and cure people of tremendous pain that they suffer from every day for years! Don’t underestimate the little ugly creatures. This reminds me of an urdu sher:

Hairat se yuun na dekhiye, zarra hua to kya hua!

Apni jagah pe janeman zarra bhi aaftaab hai.

( don’t look at it with disdain, though it may appear no more than a speck of dust to you!

But remember that in its place the speck of dust is no less important  or amazing than the enormous sun)

Kanwar

============= ============ =================== ============== ========= =====

Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun

====== ======= =========== ============================== =============

Original Antigenic Sin

Friends,

I read a very interesting article in a recent issue of the Scientific American and I thought that I should tell you about it. The article was about a very interesting concept known as “Original Antigenic Sin” and it changed the way I look at how our immunity is formed and how it develops as we grow older. Let me also take this as a opportunity to recommend the Scientific American. It is fantastic magazine and if you have a love for science or want to inculcate the love of science in your family, you must subscribe to it.

Immunity is a fascinating concept. It is also a generally misunderstood concept. How do we become immune to something during our lifetime? What is the role of the environment in creating immunity against a certain disease or pathogen? Can we acquire immunity against a new disease when we become old? How much time after the beginning of a disease do we acquire an immunity against it? There are all very interesting questions. These are also very important questions because we are surrounded by new diseases like Ebola, swine flu and bird flu. And there are many other diseases which are on the verge of making a jump from other animals to humans by a slight change in their genetic code- a mutation. We absolutely need to know how immunity is developed if we want to save the billions of people on earth from global epidemics caused by crowded cities and the fact that millions of us travel everyday taking with us pathogens and diseases.

Before I read about the concept of Original Antigenic Sin, I thought that immunity can be built at any time during one’s life. I also assumed that if one is immune to some disease, and if a new disease strikes, the immunity can be built for the new disease without being biased by past immunities. But Original Antigenic Sin says that this is not true. The memory of earlier immunities affects the formation of immunities in the future. This effect is also known as the Hoskins’s effect.

Now let me describe Original Antigenic Sin. Let’s take two adults, Alice and Bob. Lets say that when Alice was a child she was infected with an Influenza virus of the type H7M7(I am just making up a name so as not to offend the sentiments of real diseases like H1N1 J ). Lets also assume that Bob has never had contact with H7M7 virus. When Alice was infected by the H7M7 virus her body responded by making antibodies against the antigens of the invading H7M7 virus. Lets briefly recall the terminology before proceeding further. An antigen is a substance that triggers an antibody generation. Antigens are parts of invading viruses or bacteria. For example, proteins on the surface of a bacteria are antigens. The body creates antibodies for the antigens on the germs that invade it. The antibodies have “binding sites” that allows them to bind to the antigens. The antibodies thus mark the invading germs by binding to their antigens and then the immune system unleashes its forces to kill the marked germs. Think of the antigen-antibody as a lock and key pair. The antibody that can bind to one kind of antigen cannot bind to another kind of antigen. So the body needs to make specific antibodies for the invading germ’s antigens else this system will fail because then the germs would not be marked. Now, armed with these basic concepts lets come back to our story of Alice and Bob. When Alice was infected by H7M7 in her childhood her immune system worked hard to fight the virus. It learnt to make antibodies for antigens on H7M7. After the infection was defeated the knowledge of what antibodies need to be formed for H7M7 virus was not lost. This remained with Alice’s immune system. So Alice’s immune system will always remember the H7M7 virus and antigens present on it. Alice’s immune system is always going to be prepared for H7M7 because it remembers H7M7 antigens and what antibodies to form to be able to bind to these antigens. But since Bob has never been infected by H7M7, his body does not know how to fight H7M7 ie his immune system does not know the antigens on H7M7 and what antibodies to create for these antigens.

Now lets ask: how does Alice’s immune system remember H7M7? This is done by memory B cells in her immune system. These memory B cells were formed  when H7M7 virus invaded Alice’s body and these will stay throughout her life. We all have memory B cells for every infection that has ever struck us. These cells help us to generate a fast and effective response to any infection that tries to strike us again. So Alice’s body has memory B cells for H7M7 but Bob’s body does not have memory B cells for H7M7. What will happen if H7M7 strikes Alice and Bob? You would agree that Alice’s body is prepared. Her immune system knows H7M7 antigens because of memory B cells for this virus. Her immune system immediately acts when it sees H7M7 virus and starts creating antiboidoes that bind to H7M7 antigens. The infection is soon defeated. But Bob’s body is not prepared. His immune system has to first learn about the H7M7 antigens and only then can it form antibodies. So time is spent and during this time the infection grows. Bob’s body had to fight longer to kill H7M7 and this results in Bob being sick for a much longer time as compared to Alice.

Now we come to the interesting part. Lets say that H7M7 mutates and there is now a new strain of virus known as H8M8. And lets assume that H8M8 has invaded the bodies of Alice( who has previously been exposed to H7M7) and Bob( who has never had any contact with H7M7). Who will have a better chance of effective defence against this new strain of virus? Would Alice’s previous exposure to H7M7 help her? Or would Alice’s and Bob’s immune system take the same time to understand the new virus and fight it?

The answer is neither of these. And that is because of the very interesting concept of Original Antigenic Sin. Alice’s body had been infected by H7M7 ealier and when the immune system was fighting the H7M7 virus it made a lot of memory B cells for H7M7. These memory B cells knew about the antigens on H7M7 and could quickly help in creating antiboidies to counter H7M7. So Alice’s immune system is very effective against H7M7. But this knowledge of H7M7 actually puts Alice at a disadvantage against the new strain of virus H8M8. When H8M8 enters Alice’s body, the memory B cells for H7M7 become active. The body thinks that H7M7 is the culprit, it does not realize that the virus has mutated. So when memory B cells for H7M7 become active they produce antibodies for H7M7 antigens. But the H7M7 antibodies cannot bind to H8M8 antigens because the mutation has changed the antigens on H8M8. So Alice’s immune system is completely ineffective against H8M8. Not only that, her immune’s system’s knowledge of H7M7 ( from memory B cells) causes the response to be wrong. Alice’s body wastes a lot of time in countering H8M8 with completely ineffective H7M7 antibodies. This allows H8M8 to grow and cause a lot of damage. On the other hand Bob’s immune system does not have prior knowledge of any flu virus and so can start understaning the antigens on H8M8 and then create an effective response in terms of antibodies. So Bob’s body responds better to H8M8 than Alice.

So the theory of Original Antigenic Sin refers to the ineffective response given to a new mutated virus because the immune system is trying to create antibodies of a virus that it had encountered earlier. This is similar to the adage that generals always fight the last war ie if a general has won a war he will keep using the same tactics in future wars even if those tactics are not suitable in the new situation.

The concept of Original Antigenic Sin is very important for vaccine research. If we make a vaccine for a particular strain of virus or bacteria, it may make people resistant for that specific virus or bacteria. But when that virus or bacteria mutates, the person who has been vaccinated would suffer the bad effects of the disease even more than the person who has never received the vaccine.

Kanwar

============= ============ =================== ============== ========= =====

Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun

====== ======= =========== ============================== =============

Expanding the alphabet of Life

Friends,

Imagine this: you go to a strange island and find that the inhabitants have their own language. You visit their library and you find millions of books written in their language. Amazed by the size of the library and the number of books you randomly pick up a book and open it. You see something very strange: There are only 4 symbols in that book: a, t, c and g. You are also astonished to see that the letter “a” always occurs next to “t” and “c” only next to “g”. Then you pick up another book and you see the same thing. The whole library consisting of several million books has been written in a language consisting of only 4 letters and with strict restrictions of what letter can occur next to which one. You then wonder that if this amazing civilization can create so much literature out of only 4 characters, what would happen if more letters can be introduced into their alphabet. You rush out of the library to try and convince the chief of the island to include a few more letters. You are confident that the literature produced by the people of this island would be massively enriched if they expand their alphabet.

Now you may wonder why I want you to imagine such an island and you may say that it is silly to think of millions of books written using only 4 letters. But friends, the story may be fictional but its core theme is very closely related a very important true story: the story of life itself. The DNA of every living organism in the world consists of 4 nucleobases: Adenine(A), Thymine(T), Cytosine(C) and Guanine(G). So one can say that the information in a DNA is coded in terms of these 4 nucleobases. As we all know: a DNA consists of 2 strands.  You can think of these strands as sequences of nucleobases( for simplicity we will use the word bases for the rest of the article). Each base in one DNA strand is bound to a base in the other strand using chemical bonds. But the bonding between a base from one strand and that on another cannot be between any two bases: Thymine can only bind to Adenine and Cytosine can only bind to Guanine. So if one strand contains the sequence ATTCGG the second strand must contain the sequence TAAGCC.

So we see that the incredible amount of information found in the DNA of each organism that lives or ever lived on Earth is coded using only 4 letters: A, T, C and G and the letters can only occur in fixed ways: A can only occur next to T and C and only occur next to G. So the situation is very similar to the imaginary island and the incredibly interesting library that we discussed earlier. And now comes the real topic of this VERITAS: Can we increase the alphabet in the library of life and create even more complex and interesting books( organisms). Can we expand the vocabulary of life and create new “words” that benefit us? Are the bases in DNA special or can we make new ones(artificial ones)? And most importantly, if we add new letters to the alphabet of life will we be interfering with nature? There are two important properties of DNA bases/base pairs that artificial bases must have:

  • The bonds between A-T and C-G base pairs are such that the distance between the two strands of the DNA are always constant. If the A-T bond pulled the DNA strands closer than the C-G bond, the two strands could touch each other and this would be very complicated for replication.
  • A DNA must be able to replicate. DNA replication is the basis of all biological inheritance. Briefly this is how it works:  The two strands of the DNA are unwound. Each strand of the DNA now acts as the template for the creation of a new “partner” strand. So the two strands of a DNA are able to create two identical DNA double helix by first unwinding the strands and then synthesizing new strands. To give you a simplified example: Lets take the DNA strand from the earlier example that has the following base sequence: ATTCGG. The second strand would have TAAGCC. Before replication the two are connected like this :

A-T

T-A

T-A

C-G

G-C

G-C

During the replication process the two strands are first separated and so we get ATTCGG and TAAGCC as two separate unconnected strands. And then enzymes synthesize a new TAAGCC to couple with the first and a new ATTCGG to couple with the second. So we will get two DNAs which are identical to the original DNA.

So if we create new base pairs they must be able to maintain the same distance between the DNA strands as A-T and C-G. Also enzymes should be able to properly replicate them. Now replication can be challenging because the enzymes need to synthesize new bases to match the original ones. Enzymes know how to synthesize A, T, C and G. But how will we “teach” them to make the new bases that we introduce?

Scientists have been trying to create artificial bases for over 20 years now. After many years of failure scientists were able to make bases which could be placed alongside the natural bases in a DNA. Many bases and base pairs were created, some more successful than others. The best performing base pairs consisted of two mulecules called d5SICS and dNAM- Lets give them a short name: K and L ( in the original paper scientists called them X and Y but I don’t want you to confuse them with X and Y chromosomes. So I am using K and L). Now, creating a molecule that bonds with another molecule in a lab is one thing. But we want to do something far more complex- we want to add to the alphabet of inheritance and thus of life itself. So the “real” experiment needs to be done in a real cell.

And a real experiment was conducted recently. Scientists added K and L pairs to the DNA of a E. Coli bacteria. Now adding base pairs to a living cell is a challenge in itself. For this scientists relied on a “transporter” which they obtained from some algae. So the “transporter” is responsible for bringing artificial bases into the cell. Once the artificial bases were in place the DNA of the E. Coli had a mix of natural and artificial bases. So, for example, the E.Coli could have ATTKLCGG in one strand and TAALKGCC in the other( K only binds to L just like T only binds to A and C only to G). This was a major breakthrough! We had a living cell with some natural and some artificial bases in the DNA.

But the biggest success was still to come. Scientists were astonished to find that when the DNA was replicated, not only were the natural bases faithfully recreated, but the artificial bases were also replicated by the enzymes! So once you get the artificial bases into the DNA the enzymes can replicate the DNA properly and the artificial base pairs will go to future generations also. Scientists observed that the artificial bases were carried intact generation after generation of the bacteria.

So this really is a very exciting breakthrough. We can expand the alphabet of life! And we can expand it in such a way that it benefits us. When we add information to DNA we can add it in such a way that it helps us- we could create new vaccines, we could create new drugs, we could destroy certain diseases- the possibilities are endless. Of course, knowledge without wisdom can be a dangerous thing. So if we are to change the basic structures of life itself, we better do it carefully and with the intention of improving the beauty and diversity of life and not solely for profit.

Regards

Kanwar

============= ============ =================== ============== ========= =====

Go wondrous creature, mount where science guides

go measure earth, weigh air, state the tides,

instruct the planets in what orbs to run

correct old time, regulate the sun

====== ======= =========== ============================== =============

Hargobind Khorana

In a recent discussion with some friends the topic drifted to Indian Nobel Prize winners. Almost everyone seemed to know about C.V Raman, or Rabrindranath Tagore and about Subramanian Chandershekhar and also their contributions. But very few of us knew much about Dr Hargobind Khorana and his contributions towards Science. In today’s VERITAS we will try to correct this situation.

 

        Dr Hargobind Khorana was born in 1922 at Raipur, Punjab ( this is now in Pakistan). He was born in a poor family. His father was a “patwari”

in the village. A “patwari” is an agrigulture tax collector. This is a post that is still common in Punjab villages. He was the youngest in the family of 5 children. Hargobind Khorana attended D.A.V high school in Multan. Later he studied in Punjab University at Lahore and got the MSc degree. He got a scholarship to study in England. He joined the University of Liverpool and got the Phd degree in 1948. IN 1949 he returned to India. He tried desperately to search for a job but he could not find one. He returned to England and joined Cambridge.

 

        At Cambridge Hargobind Khorana became interested in proteins and nucleic acids(DNA and RNA). He moved to Canada in 1952 and joined the University of British Columbia. In 1968 Khorana received the Nobel Prize in Physiology and Medicine along with Nirenberg and Holley. They were awarded the Nobel Prize for their research which led to deciphering of  the Genetic Code and helped understand its function in protein synthesis.

 

        Lets understand this in more detail. In 1944 Avery showed that genes are made up of Nucleic acids. Both DNA and RNA are composed of 4 nucleotide bases. DNA is composed of adenine(A), Guanine(G), Cytosine(C) and Thymine(T). DNA is composed of strings of these bases. So a DNA strand may look like AATGGGTTACCC etc. Nirenberg was the first to show that each set of 3 bases like AAA or GGG etc forms an amino acid. He formed an artificial DNA by constructing a string of a single repeating base. So Nirenberg showed how DNA/RNA is composed of repeating bases. Khorana developed this work independently and decipered the codes for several known amino acids. He discovered for example that the amino acid Glycine was  GGA etc. He did this by constructing giant nucleic acids( giant DNA and RNA) with complicated base strings. Holley succeeded in preparing something known as transfer-RNA and determined its exact structure.

Transfer-RNA is a special type of nucleic acid. It has the ability of reading genetic code from somewhere else and transforming it to form a protein.

So Hargobind Khorana was one of the scientists who succeeded in understanding the alphabet which is used to create DNA and RNA. He also managed to create DNA and RNA in his laboratory. So Hargobind Khorana is one of the pioneers of Genetic Engineering.

        Hargobind Khorana is still doing active research. I went to his webpage in the “faculty and research” section of MIT’s chemistry department. He is currently doing research on molecules that act as receptors of light in the eye- Rhodopsin, 11-cis-retinal, all-trans retinal( See VERITAS: Light and Life Part II, May 12, 2005 for details on these molecules and the bio-chemical mechanism of sight).

 

Kanwar

 

|======================================================|

  Go, wondrous creature! mount where Science guides:                 

  Go, measure earth, weigh air, and state the tides:                 

  Instruct the planets in what orbs to run,                          

  Correct old time and regulate the Sun;                             

|======================================================|

A Strange Animal

 

    Yesterday while watching Discovery Channel I learnt about a very strange creature . DO you know that there is only one mammal that is poisonous and it is the   Platypus .

      And this is not the only thing that is strange about it . The Platypus is found only in eastern Australia . They lives on the edges of rivers and lakes . Platypus are excellent swimmers and can stay underwater for 3 to 5 minutes . Platypus must continuously swim downwards with its forefeet to remain submerged . They only way it can rest underwater  is by resting under submerged rocks . The Platypus closes its eyes and ears once underwater . Then how does it catch its prey ( snails , shrimps etc ) ? It does so using its very sensitive duck like snout and by electric navigation . It does not eat its food underwater . It stores it in the folds in its cheeks and eats it once it comes back to the surface .

      A platypus is about 60 centimetres in length and weighs about 2 kgs . The male platypus has two sharp , hollow , horny spurs(projections) on its hind legs . These are connected to poison glands . They have enough poison to kill a man . Platypus “stings” are extremely painful . Females dont have poison glands or spurs so the main function of spurs in the male platypus is during fights over female platypus .

      Another funny thing about the platypus is that it is a mammal but it lays eggs ! The only other mammal that lays eggs is the Echidna ( a small animal found in Australia ) . Such mammals are called monoterms .

      The platypus females dont have any teats . They ooze the milk from the fur and the platypus young lick off it .

      Platypus have a beak which resembles duck beaks . So it almost looks like a cross between the birds and the mammals .

 The platypus’s red blood cells carry larger amounts of hemoglobin than any other mammal . This allows the platypus to go without air for longer periods. The heart rate of a platypus can drop from 140 – 230 beats a minute to almost 0 beats per minute .

 

            I found a nice little poem on written by Ogden Nash (who also happens to be my favourite poet ) .

PS : anomalous means having an anomaly ( defect ) , platitude means dullness .

 

                  The Platypus     by Ogden Nash

                  =============

  I like the duck billed platypus

  Because it is anomalous

  I like the way it raises it family

  Partly birdly , partly mammaly

  I like its independent attitude

  Let no one call it duck billed platitude .

 

 

Enjoy,

Kanwar

Harvey and the circulation of Blood

 

      The circling streams once thought but pools of blood

      Whether life’s food or body’s fuel

      From dark oblivion Harvey’s name shall save

 

                              – Dryden

 

      Around the same time when Newton was making his making his mathematical theories and Shakesphere was writing his great tragedies , there was another man in England who was making some breakthrough theories in the field of Madicine . His name was William Harvey .

      At that time all we know about the circulation of blood in our body was from the theories of Galen,the Greek physician who lived in the 2nd century He dissected the body and made the first theories of blood formation and how it flows in the body .

      Before Harvey people believed that food was converted to blood in the liver and blood is the food for various organs in the body . The role of the heart was unclear .

 

      Harvey was born in Folkeston in 1578 . He graduated to become a physician from Cambridge University . He then went to Padua University in Italy for further study of medicine . Here he studied the theories of Galen . In 1604 he returned to England and started practicing as a doctor .

In 1615 he bacame a lecturer in surgury . This position required Harvey to do various public dissections . It was during this time that he started stating his theories about the circulation of blood .

      His methods were different . He didnt start with the human body .

He believed that in order to understand how complex systems behaved it is first important to study simpler creatures . So he started studying frogs , snails , lobsters etc . He found that all blood vessels start from the heart . Also all blood vessels pass thru the lungs . So he was the first to say that the heart is the “machine” that pumps blood into the body . He considered the heart to be a muscle the contraction of which pushes blood in the artries . He was the first to show that blood goes to different parts thru the artries and comes back through the veins .

So the circulatory system is a circular one way path . He disproved Galen’s throry that veins take blood to the different parts of the body .

This he showed by observing the valves in the veins and in which direction they open .

      Of course some of his theories were wrong too . He tried to make a theory which could explain the difference in color of the blood in the veins and the artries . But he was wrong . The actual theory came after oxidation was discovered .

      He published his theories in 1628 in ” An Anatomical study of the Motion of Heart and Blood in ANimals ” . His theories met with stiff resistance . One of his opponents ( Hoffman ) said that if Harvey’s theories are to be believed then that would mean that there are 2 kinds of blood ( pure and impure ) . But how can this be true . Nature prefers simplicity . Then there were others who tried to invoke religious huga – buga ! But all in vain ( artery ?! ) . Harvey had answers to all their issues .

      His theories are now an integral part of Madicine . He was the first person after Galen to make a good theory about blood circulation because he believed in experimenting and not just thinking about what should be the truth . This method of experimentation was what started the Scientific revolution .

      After his research on blood circulation he made some discoveries in embryology . His research in this area proved the basis for modern theories in this area .

 

      He died in 1657 .